document.getElementById().src audio issue

Question

What am I doing wrong here? (see JS Fiddle: http://jsfiddle.net/55aJt/6/)

<audio id="myAudio" src="" controls></audio>

Object

var allQuestions = [{
    question: "http://www.w3schools.com/html/horse.mp3",
    choices: ["3rd", "5th", "4th"],
    correctAnswer: 2
},

Function

function setHeader(questionNum) {
    var questionHeaderEl = document.getElementById("myAudio").src;
    questionHeaderEl.innerHTML = allQuestions[questionNum].question;
}

Answer 1

var questionHeaderEl = document.getElementById("myAudio").src;
questionHeaderEl.innerHTML = allQuestions[questionNum].question;   

with above code you are creating a var for element's src value then you are trying change innerHtml of that src value. It should be like this:

var questionHeaderEl = document.getElementById("myAudio");
questionHeaderEl.src = allQuestions[questionNum].question;

Answer 2

use

questionHeaderEl.src 

instead of

questionHeaderEl.innerHTML